Mżrdalsjökull is an the fourth largest ice cap in Iceland with a total area of 600 km2 and a mean ice thickness of 230 m. The ice cap is underlain by a highly active central volcano (named Katla) containing a large caldera. The caldera encircles an area of 100 km2, is 600 to 750 m deep and its highest rims reach 1380 m a.s.l.

Latitude (°, cent):

63.68

Longitude (°, cent):

19.05

Surface (km2):

600

Lenght (km):

Width (km):

26

Min. altitude (m):

120

Max. altitude (m):

1510

Orientation (°)

Slope (°)

EVENT: Date
25/6/1955
- Date quality:Duration: 10 hours

Type:

Glacier flood (contain both lakes and water pocket)

Description

A small jökulhlaup that originated from one of the cauldrons. The water broke through at the soutwestern terminus of the Outlet glacier Kötlujökull and flooded part of the outwash plain Mżrdalssandur.

Effects:

Volume: ca. 28 million m3.

Deaths(#)

0

Injuried (#)

0

Note

People expected this jökulhlaup to be preceeding a volcanic eruption. The news reached about all country except for 4 men researching the ice thickness on Mżrdalsjökull itself. Luckily no eruption followed this jökulhlaup.

About 7 hours before an eruption column could be seen on the ice cap Mżrdalsjökull an earthquake shook the area. Some hours later a tremendous jökulhlaup broke through the Outlet glacier of Kötlujökull and flooded all Mżrdalssandur.

Effects:

The jökulhlaup was first noticed at Hjörleifshöfda at noon, the peak discharge of 100.000 to 300.000 m3/s was reached 2,5 hours later. The south coast was extended by 3 km by the laharic flood deposits. Icebergs, up to 40 m high covered Mżrdalssandur after the flood.

Due to a volcanic eruption beneath the ice cap Mżrdalsjökull, meltwater found its way through the Outlet glacier Kötlujökull and flooded part of the outwash plain Mżrdalssandur.

Effects:

Eruption lasted about 120 days. It started with earthquakes before noon on 17 oct. The eruption coloumn could be seen late afternoon, and the jökulhlaup started in the evening and lasted over the next night. It“s main path was west of mt. Hafursey, but it also flooded river Hólmsį and the southeastern part of the outwash plain.

Deaths(#)

0

Injuried (#)

0

Note

This eruption was the fourth largest tephra eruption scince Iceland was settled (with an estimated ash volume of 1500 million m3). 50 farms were destroyed because of the ash layer.

Due to a volcanic eruption beneath the ice cap Mżrdalsjökull, meltwater found its way through the Outlet glacier Kötlujökull and flooded part of the outwash plain Mżrdalssandur.

Effects:

The jökulhlaup reached its peak discharge (200.000 to 300.000 m3/s) within a very short time from its beginning. It reached the ocean with such pressure, that a small tsunami hit the harbour of the westmen islands (about 80 km west of Katlatangi). Close to the farm Hjörleifshöfša (which was -as the last farm on the western Mżrdalssandur- distroyed in this flood) a rock, 20 m high and quiet broad, was taken by the jökulhlaup. The woman and her young child who lived on the farm reached a small cave for shelter.

Deaths(#)

0

Injuried (#)

0

Note

Eruption lasted more than 100 days. The total volume of tephra and ash was close to 1 km3.

Due to a volcanic eruption beneath the ice cap Mżrdalsjökull, meltwater found its way through the Outlet glacier Kötlujökull and flooded part of the outwash plain Mżrdalssandur.

Effects:

The main jökulhlaup flooded a huge part of Mżrdalssandur on 3. Nov. Fertile land was destroyed and could not be used for years. On 8 nov the flood took the church and farmhouse Höfdabrekka, they were rebuild on a higher location.

Due to a volcanic eruption beneath the ice cap Mżrdalsjökull, meltwater found its way through the Outlet glacier Kötlujökull and flooded part of the outwash plain Mżrdalssandur.

Effects:

The jökulhlaup is just mentioned by year (Thorsteinn Magnusson, head of the monastery of Thykkvabęr).

Deaths(#)

0

Injuried (#)

0

Note

First one could read about an eruption beneath the ice cap Eyjafjallajökull, which is directly west of Mżrdalsjökull. Today it is quiet sure, that this eruption occurred beneath Mżrdalsjökull. A reference to the jökulhlaup exists (from the head of the

Due to a volcanic eruption beneath the ice cap Mżrdalsjökull, meltwater found its way through the Outlet glacier Kötlujökull and flooded part of the outwash plain Mżrdalssandur.

Effects:

This is the first time in the icelandic history that a jökulhlaup is mentioned and described. The flood had swept away several farms and two churches.
Probably the flood destroyed an old harbour near to Mt Hjörleifshöfda in the fjord Kerlingafjörd sem today is completely vanished.

Deaths(#)

0

Injuried (#)

0

Note

The old referece: Thorlįkur bishop travelled to Jon Loftsson on the farm Höfdabrekka, where they mentioned the loss of farms.